feat: ComfyUI embedded dev setup + proxy auth with downstream keys

- COMFYUI_BASE configurable via env var (default 127.0.0.1:8188)
- All /api/comfyui/ routes protected by downstream API Key or admin token
- docker/Dockerfile.comfyui + docker-compose.comfyui.yml for dev
- npm scripts: comfyui:install, comfyui:start, comfyui:stop
- .gitignore / .env.example updated

.env.example

@@ -28,3 +28,6 @@ DATA_DIR=./data
 NOTIFY_COOLDOWN_SEC=300
 ADMIN_IP_ALLOWLIST=
 TZ=Asia/Shanghai
+
+# ComfyUI — 本地工作流引擎地址（默认 http://127.0.0.1:8188）
+COMFYUI_BASE=http://127.0.0.1:8188